1. Field of the Invention
This invention relates to a specific optically active compound. More particularly, it relates to a compound having asymmetric carbon atoms.
2. Description of the Prior Art
Liquid crystals are widely applied to various electrochemical devices and thus employed in practice in display devices of, for example, clocks and electric calculators. Most of liquid crystal display devices commonly used today take advantage of the dielectric alignment effects of twist-nematic or cholesteric liquid crystals. Recently, however, it has been vigorously attempted to develop liquid crystal display systems other than those mentioned above. Examples of these new systems include a STN system and a cholesteric/nematic phase transistion system.
Each liquid crystal composition to be employed in these liquid crystal display devices is adjusted in such a manner as to give the corresponding helical pitch by introducing an optically active group to nematic liquid crystals or adding an optically active substance thereto.
A typical example of such a liquid crystal composition as described above is Shiff base liquid crystals prepared from a p-alkoxybenzaldehyde and (+)-p-amino-2-methylbutylbenzene. A 4-(2-methylbutyloxy)-4'-cyanobiphenyl compound is known as the optically active substance to be added to liquid crystals. However this compound is disadvantageous in that it should be added in a large amount in order to achieve the desired properties, since it has a long helical pitch of cholesteric liquid crystals.